1. Field of the Invention
The present invention relates to an automatic transmission for a vehicle. More particularly, the present invention relates to a planetary gear train of an automatic transmission for a vehicle that may improve power delivery performance and reduce fuel consumption.
2. Description of Related Art
Increase of gas price may be factor that drives competition for enhancement of fuel consumption.
For an engine, research is made for weight reduction and enhancement of fuel consumption by down-sizing, and for an automatic transmission, research is made for achieving drivability and fuel consumption competitiveness by achieving more multi-stage of the transmission.
However, when an automatic transmission has more shift stages, it requires more number of parts and may deteriorate installability, weight, efficiency, etc.
Thus, in order to effectively achieve enhancement of fuel consumption by achieving more shift-stages, it is important to develop a planetary gear train that may become more efficient with less number of employed parts.
In this regard, an eight speed or nine speed automatic transmission is recently realized, and a planetary gear train of even more speeds is under investigation.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.